In a subgroup analysis of the ‘Positron Emission Tomography-Guided Therapy of Aggressive Non-Hodgkin Lymphomas’ (PETAL) trial [2] we showed that interim [18F]fluoro-deoxyglucose-positron emission tomography/computed tomography ([18F]-FDG-PET/CT) predicts outcome in all major PTCL subtypes except anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) which has a much better prognosis than the other entities [3]. The gene discussed is ALK; the disease is non-Hodgkin lymphoma.